1. Field of the Invention
This invention relates to specifically to arrays of pre-fabricated structural panels to improve the efficacy of daylighting, heating, ventilation and air conditioning systems used in building operations.
2. Description of the Prior Art
Key metal building roofing improvements of in the areas of reducing moisture vapor permeation of through the roof deck, (to limit corrosion and maintain insulation values) and improving roof insulation, are not addressed in many current metal building roof decks. One area of the prior art in double roof plenum air source solar collectors such as Pulver (U.S. Pat. No. 3,994,276) and Johnson (U.S. Pat. No. 4,054,246) exacerbates these problems. While the roof deck amounts to about 23% of heating load in commercial buildings, the net effect is very small on the cooling load in commercial buildings (Huang 1999 and FIGS. 10a, 10b). Because of poor insulation in commercial roofing, typically R-9.9, the net effect of the roof deck on cooling load is negligible compared to other loads such as equipment (Lee 2013), lighting, and vertical glazing.
Cooling as a major peak summer load factor, along with daytime lighting can be seen as the major cause of grid failures/brownouts and is very important to a number of cooling intensive applications e.g. computer server centers, retail stores, offices, hospitals and supermarkets.
While Hartman (U.S. Pat. No. 6,959,520) effectively addresses the issues of improved insulation and vapor transmission/corrosion; the daylighting section there uses air flow between an upper and lower glazing for the primary purpose of removing heat buildup from that section i.e. not melting the thermoplastic upper glazing. Venetian blind louvers are used between the two glazing lites to modulate entry of both visible and infrared (IR) components of natural light entry into the building envelope. Either or both of these strategies/equipment approaches are used in the prior art of Murray (U.S. Pat. No. 4,730,552), Howe (U.S. Pat. No. 4,577,619), Cummings (RE 33,720) Dittmer (U.S. Pat. No. 5,062,247), Ayles (U.S. Pat. No. 5,435,780), Kastner (U.S. Pat. No. 8,068,282) and surprisingly the 2008 state of the art NY Times facility, (Lee, 2013). Miller (U.S. Pat. No. 4,468,899) and Christopher (U.S. Pat. No. 5,617,682) do not provide for movement of air between two parallel glazing components.
While the Times facility is not a systems or low-slope flat roof building, some important figures highlight the interactions between artificial/natural lighting, the advanced under floor air HVAC supply method and the cooling load. In a bar chart comparison to an ASHRAE 90.1-2001 compliant system, the new system showed very little reduction in cooling load, although the electrical lighting load was reduced to 56% of the control case. Daylighting influx of heat is the logical source of this equal cooling load as equipment demands are the same and waste heat from the artificial lighting has dropped.
Artificial and natural lighting make up between 87% and 97% of the total cooling load loads in commercial buildings with other factors such as the floor, building envelope, air infiltration, equipment and occupants being of a lower magnitude and acting to cancel each other out, FIGS. 10a/10b. In direct sunlight, only about 45% of the energy is in the visible part of the spectrum, while diffuse light (cloudier conditions, North light and winter) contains about 75% of the energy in the visible spectrum, (Duffle, 1991). The balance between shorter days during the heating season and increased visible content comes into play and moves daylighting performance toward a more equal footing (with the same roof daylighting aperture) between the seasons when IR filtering is used. Improved daylighting, heating and cooling systems for commercial structures should take these factors into account, ideally as integrated building envelope solutions.
In general, the double dome skylights commonly used to illuminate the interior of flat roof buildings do not filter the infrared component of exterior light. They therefore do not afford a significant improvement in air conditioning loading over artificial lighting. Double wall acrylic or polycarbonate plastic prior art leading to the present offerings includes examples such as York (U.S. Pat. No. 6,695,692). For this reason, daylighting codes, (where they are present), limit the percentage of daylighting aperture to 5% of the roof to prevent excessive cooling demand additions, [e.g. California Title 24]. California code recognizes the importance of daylighting in big box stores by requiring daylighting in any ‘room’ over 25,000 SF. It does not take into account IR filtering at present.
Several skylight systems using a roof mounted dome communicating through a reflective tube to a ceiling fixture, (primarily used in residential or low rise wooden construction) do have IR rejection built into the system. Representative prior art in this area is Jaster (U.S. Pat. No. 7,954,281). Parallel flat plate glazing of this type is represented by Dittmer (U.S. Pat. No. 5,062,247). Both these devices simply vent heated air flow to the exterior, rather than managing the use of the heat inside when it might be needed, again primarily using air flow to prevent melting of outer glazing. Jain (U.S. Pat. No. 6,014,845) uses an unusual diffract grating solution with only one (outer) glazing.
Other prior art that does not deal with infrared rejection but uses parallel room ventilation with separate glazing units is seen in York (U.S. Pat. No. 6,695,692) and Han (U.S. Pat. No. 6,142,645). In the mix of many very similar elements of prior art in the area of skylights and ventilating devices what is missing is a system focused on day to day and season to season heating and particularly cooling needs.
Daylighting curbs in the prior art are not often utilized for sloped roof building applications because of a difficult transition and sealing task between commonly used standing seam roof surfaces and the curbs. They are rarely used in retrofit applications for flat roofs as the sealing of the field cut hole for the device is another area of concern. Positive sealing of the glazing against the roof deck is therefore an important property for any improved daylighting/HVAC system.
Bringing some of the features of an improved system to bear on utilizing night sky cooling techniques, (Martin, 1984), the system could be utilized in a wide variety of buildings with high cooling needs, such as supermarkets and computer server facilities. This would also expand on the very early prior art of solar pioneer Harold Hay in this area.